NEW YORK — NASA’s defunct UARS climate satellite fell back to Earth Sept. 24 over an uninhabited stretch of the South Pacific, U.S. tracking experts eventually determined.
The 6.5-ton Upper Atmosphere Research Satellite, or UARS, plunged through the atmosphere at 12:01 EDT, NASA officials said.
The Joint Space Operations Center at Vandenberg Air Force Base in California said the satellite entered the atmosphere over the Pacific at 14.1 degrees south latitude and 189.8 degrees east longitude, NASA said in a “final update” posted Sept. 27 on its website. “This location is over a broad, remote ocean area in the Southern Hemisphere, far from any major land mass.”
The spacecraft was the largest NASA satellite to fall uncontrolled from space in 32 years. So far, there is no evidence that anyone was harmed by falling UARS debris.
“NASA is not aware of any reports of injury or property damage,” officials wrote in a statement.
The doomed satellite plummeted through Earth’s atmosphere hours later than scientists had originally predicted, but despite its uncontrolled re-entry, agency officials maintained throughout that the risk to public safety was very remote.
NASA and the U.S. Air Force had been closely monitoring the UARS satellite, and increased solar activity during the week caused the dead spacecraft to plummet faster than was originally expected. As a result, agency officials projected that UARS would fall to Earth sometime during the afternoon of Sept. 24, but the satellite’s tumbling, combined with more stable solar activity, slowed the spacecraft’s rate of descent.
NASA estimated that roughly 26 large pieces of the spacecraft would survive the re-entry process to be strewn over a 804-kilometer path. The largest piece of debris was expected to be approximately 135 kilograms.
In its Sept. 27 update, NASA said the debris field was located between 480 kilometers and 1,300 kilometers downrange, or generally northeast of the satellite’s re-entry point.
“NASA is not aware of any possible debris sightings from this geographic area,” the update said.
NASA has advised that when it comes to satellite remnants, it is not a case of finder’s keepers. In fact, the agency urged anyone who comes across what they think is a piece of the UARS satellite, however unlikely, to leave it where it is and contact local authorities.
“Just remember, ‘not UARS — or rather, yours — to keep,’” space artifacts expert Robert Pearlman, editor of the website collectSPACE.com, said. “Should the public come across debris they believe to be from the downed satellite, they should alert the authorities, or the authorities may come after them.”
Even if it is in fragments, the UARS satellite is still property of NASA and the U.S. government, Pearlman added, which makes the debris off limits for anyone thinking of keeping a piece as a souvenir.
“Regardless of where it falls, in or outside the borders of the nation, the U.S. has first right of refusal on any remnants, as either enforced by U.S. law or a United Nations treaty,” Pearlman said.
But apart from the legal aspect, NASA’s advice to not touch any potential pieces of satellite debris is also for safety reasons.
“Though UARS has no harmful chemicals or radiological material aboard, the nature of it being ripped apart during re-entry may have formed sharp, jagged edges,” Pearlman said. “NASA doesn’t want to see anyone inadvertently harmed while trying to collect a souvenir.”
As UARS’s orbit decayed, some folks hoped the spacecraft’s fiery demise would bring about a brilliant light show. At least one pair of lucky skywatchers in Florida were able to catch a glimpse of the doomed satellite as it circled the Earth before its final descent.
Thomas Marxo Jr. said he and his wife spotted the UARS satellite the evening of Sept. 23 as it cruised overhead to the east of South Florida. Marxo had researched the time when the spacecraft was slated to make an orbital pass, but because of cloudy skies, was about to give up when he saw the dying satellite streak across the sky.
“It was very bright and traveling at a greater speed than any of the other satellites that I have observed,” Marxo said in an email. “I feel as if I have observed a part of history that I can tell the grandkids about someday.”
The $750 million UARS satellite is the largest NASA satellite to fall uncontrolled from space since 1979. Skylab, the first U.S. space station, plummeted to Earth in 1979, and debris from the complex plunged into the Indian Ocean and onto parts of Australia.
Also in 1979, NASA’s Pegasus 2 satellite, which was almost twice the mass of UARS, made an uncontrolled splashdown in the middle of the Atlantic Ocean. Pegasus 2 was launched in 1965 to study micrometeoroids in low Earth orbit.
UARS was launched in 1991 aboard the space shuttle Discovery to study the ozone layer and the chemical makeup of Earth’s upper atmosphere. The satellite measured 10.7 meters long and 4.5 meters wide. NASA decommissioned the satellite in December 2005.
Despite UARS’s uncontrolled re-entry, NASA maintained that the chance of any pieces of the satellite falling on a densely populated area was extremely remote. To date, there have been no reported injuries or casualties from re-entering satellites or spacecraft.
In 1997, however, Lottie Williams of Tulsa, Okla., reported that she was struck on the shoulder by falling space junk while out walking. The debris was later confirmed to have been part of a fuel tank from a Delta 2 rocket, and other pieces of the booster were recovered several hundred kilometers away in Texas.
Still, orbital debris experts are hoping the fall of the UARS satellite will highlight the need to promote sustainability in space.
“This is not an uncommon event; space debris is re-entering our atmosphere all the time,” William Ailor, director of the Center for Orbital and Reentry Debris Studies at The Aerospace Corp. in California, said. “We are trying to learn everything that we can about orbital and re-entry debris so that we can protect space missions and human interests on the ground.”
